WO1993015876A1

WO1993015876A1 - Spindle positioning method

Info

Publication number: WO1993015876A1
Application number: PCT/JP1993/000092
Authority: WO
Inventors: Shinichi Kono; Masaaki Fukukura
Original assignee: Fanuc Ltd
Priority date: 1992-02-14
Filing date: 1993-01-26
Publication date: 1993-08-19
Also published as: DE69309803D1; EP0580866A1; US5519297A; DE69309803T2; KR960012701B1; JPH05228794A; EP0580866A4; EP0580866B1

Abstract

A main spindle positioning method which makes the most of deceleration of a spindle motor and speeds up a spindle positioning operation. It is assumed that the spindle motor is running under speed control. In response to a command for a stop at a given position, the spindle motor is decelerated to a speed N below a maximum rotating speed N1 determining a constant torque region on the basis of the speed control (Step S1), and the speed control is switched to a position control at the position at which the speed N is reached. At this time, a value which takes into consideration the present position at one rotating position of the spindle and a target stop position as an initial position error are set to an error counter (Steps S5 to S11). Thereafter, a position feedback quantity Pf from a position sensor is received by the error counter so as to execute linear acceleration/deceleration control to a final stop position (Step S12) and a speed command Vcmd is determined (Step S13), and a speed loop processing follows.

Description

Specification

Spindle positioning method

Technical field

The present invention relates to a spindle positioning method for stably positioning and stopping at a desired position in a short time by making full use of the deceleration capability of the spindle 乇 overnight.

Background technology

As a technique for positioning and stopping the rotating spindle motor at a desired position, in the speed control stage, the speed is reduced to a base speed for positioning control, and then the spindle motor is moved to the speed control. There is known a method of switching from a state to a state of position control, performing a position loop control by setting a difference between a command stop position and a current position as a position deviation.

In order to shorten the time required for positioning by this method, it is conceivable to increase the value of the position gain.However, this method ignores the acceleration / deceleration characteristics of the spindle motor. Such processing may make it difficult for the spindle motor to follow the speed command, resulting in inadvertent overshoot. In addition, if the position gain value of the position loop is set to a small value for fear of overshoot, the time required for positioning will inevitably increase. It is difficult to realize prevention and high-speed positioning at the same time.

Disclosure of the invention

An object of the present invention is to prevent inadvertent overshoot, Another object of the present invention is to provide a spindle positioning method capable of positioning a spindle of a machine tool at a desired stop position in a short time.

In order to achieve the above object, the present invention, when a fixed position stop command is received while driving rotation control of a spindle motor based on speed control, the motor rotation speed is reduced based on the speed control. When the speed is reduced to a speed less than or equal to the maximum rotation speed that stipulates the constant torque area, and when the speed is reduced to that speed, the initial position deviation is related to the current position within one rotation of the motor and the command stop position. After the set value is set, the drive control of the motor is switched from speed control to position control, and then linear acceleration / deceleration control is performed up to the command stop position.

Further, the present invention provides a spindle positioning method for positioning a spindle at a desired rotation position, wherein when the spindle motor speed is lower than a base speed, the rotation speed of the spindle motor and the rotation position within one rotation of the spindle. Is detected, the minimum movement amount for decelerating and stopping along the deceleration straight line set based on the detection speed is obtained, and the movement amount from the detected rotation position to the target stop position is obtained. Is sequentially added to the above-mentioned movement amount until the rotation becomes larger than the above-mentioned minimum movement amount. The movement amount obtained by the addition is set as a position g deviation, and the position is obtained. The speed command is obtained by performing position loop control by multiplying the square root of the deviation by the set position loop gain, and the drive of the main spindle motor is controlled based on the speed command.

Preferably, the minimum movement amount is the square of the detection speed. The position loop gain is obtained by dividing by a preset parameter overnight value determined by a deceleration straight line, and the position loop gain is a value of the square root of the above parameter overnight.

Further, according to the present invention, (a) when a fixed position stop command is received, the rotation speed of the spindle 乇 overnight is reduced to a speed N that is equal to or less than the maximum rotation speed N1 that defines a constant torque region, and (b) Calculate the number P 1 of output rotation pulses of the position detector when rotating from the reduced rotation speed N to the final stop position at a predetermined constant gradient (deceleration), and (c) The number of forward rotations from the current in-rotation point position of the main spindle that overlaps the stop position of the main spindle is calculated using the output rotation pulse number α of the position detector, and (d) above (b) The number of pulses P1 calculated in step (c) is compared with the number of pulses α calculated in step (c). (E) If the number of pulses α is larger than the number of pulses Ρ1, the pulse The number α is the initial position deviation, and the number of pulses Ρ 1 is the number of pulses When it is equal to or larger than α, the output rotation pulse number of one revolution of the main shaft of the position detector is PreV, and for an integer n of 1 or more,

a + (n-1) · P rev <Ρ 1 ≤ α + η · When rev rev holds, α + η · P rev is set as the initial position deviation in the error count. (F) Thereafter, the number of feedback pulses P f from the position detector is subtracted from the initial deviation obtained in (c) above, and the square root of the number of pulses of the subtracted value is calculated according to the motor deceleration characteristics. Multiplied by the determined gain to obtain a speed command Then, the drive of the spindle motor is controlled based on the speed command. As described above, according to the present invention, in order to stop the spindle at the predetermined position, first, the spindle motor is decelerated to a region below the base speed at which the torque is constant. In this region, the torque is constant and linear acceleration / deceleration control is possible, so that the spindle motor is position-controlled along the predetermined deceleration straight line and stops at the final position. In the deceleration process up to the stop position, the deceleration capability of the spindle motor is utilized to the maximum, and the positioning time is shortened without causing overshoot.

Brief explanation of drawings

FIG. 1 is a block diagram showing a main part of a spindle control circuit in a machine tool according to an embodiment to which the method of the present invention is applied.

FIG. 2 is a functional block diagram showing details of the motor control circuit in the embodiment,

FIG. 3 is a flowchart showing an outline of a fixed-position stop process by the motor control circuit of the embodiment.

Fig. 4 is an operation principle diagram showing the calculation method of the parameters used in the fixed position stop processing, and

Figure 5 is a conceptual diagram showing the relationship between the current position of the spindle motor and the command stop position of the spindle.

Best Mode for Carrying Out the Invention FIG. 1 is a block diagram showing a main part of a spindle control circuit in a machine tool according to one embodiment. It is rotationally driven by the spindle motor 4 via a power transmission mechanism 2 such as a gear or timing belt. The main spindle 1 is provided with a position detector 3 that generates Prev position detection pulses per rotation and outputs a rotation signal per rotation. Further, a speed detector 5 for detecting the rotation speed of the main shaft 1 is mounted on the main shaft motor 4 for driving the main shaft 1 to rotate.

The position detector 3 and the speed detector 5 are connected to a motor control circuit 7. The spindle motor 4 is connected to a motor control circuit 7 via a power circuit 6, and the motor control circuit 7 itself is connected to a numerical control device 8 for controlling each axis of the machine tool. The motor control circuit 7 includes a speed control unit for controlling the speed of the spindle motor 4 and a position control unit for controlling the positioning stop operation, and a processor and ROM for performing various calculation processes. And a RAM, etc., and drives and controls the spindle motor 4 through a power circuit 6 such as a transistor and a transistor.

The motor control circuit 7 counts the position feedback pulse Pf output from the position detector 3 and receives a rotation signal from the position detector 3 every time it receives one rotation signal. And a latch circuit for latching the value of the power supply.

In this embodiment, the reduction ratio of the power transmission mechanism 2 is 1: 1.

Fig. 2 is a functional block diagram of the motor control circuit 7. In the figure, a is the error counter that stores the position deviation during the positioning stop operation, and b is the speed on the software. Command calculation means, c and d are proportional gains of speed control loop And integral gain. In addition, h and f are the terms of the transfer function of the spindle motor 4, Kt is the torque constant, Jm is the inertia, and g is the transfer of the integral that determines the position by integrating the speed. This is a function term. Also, S 1 and S 2 are switches shown for convenience, and are switched depending on the speed control and positioning control of the spindle 1.

Therefore, first, an outline of the operation of the present embodiment will be described. Normally, the switch S2 is turned off and the switch S1 is turned on. Speed control is performed based on the rotation speed command VciID sent from the controller. That is, a speed deviation is obtained by subtracting the speed feedback signal Vf output from the speed detector 5 from the rotation speed command Vcmd, and multiplying this speed difference by the speed loop proportional gain c. The value obtained by multiplying the value obtained by integrating the speed deviation and the value obtained by multiplying the value obtained by multiplying the speed loop integration gain d to obtain a torque command, and drive-controls the spindle motor 4 via the power circuit 6. Processing is performed.

On the other hand, if the positioning stop command and the spindle stop position (rotational position within one rotation) are output from the numerical controller 8, the processor of the motor control circuit 7 is shown in Fig. 3 Flow chart. `` Motion stop processing '' (details will be described later) is started to control the motor 4 while maximizing the deceleration capacity of the main vehicle, while preventing overshoot. The spindle will be positioned at the command stop position.

First, using the principle of operation shown in Fig. 4, fixed-position stop control is performed in a state where the above-mentioned motor deceleration capacity is maximized. Explain how to find the parameters needed to perform the task.

First, the spindle motor 4 has a constant torque in a region below a certain rotational speed .N1 (rpm), and linear acceleration / deceleration control is possible in that region. Hereinafter, the rotation speed N 1 (rpm), that is, the maximum rotation speed per minute at which the Tonnolek--constant region is given, is referred to as a base speed N 1. If this linear acceleration / deceleration control is illustrated in the graph of Fig. 4 with the horizontal axis representing time and the vertical axis representing rotation speed, the deceleration operation follows the straight line L (deceleration straight line) in the figure. .

In FIG. 4, the stop time required when the spindle motor 4 is stopped at the maximum deceleration operation from the base speed N 1 is defined as T 1, while an arbitrary rotation speed N (rpm) less than the base speed N 1 is set. Assuming that the time required to stop the spindle motor 4 along the deceleration straight line L from T is T, the slope (deceleration) of the deceleration straight line L is constant, and the following relationship is obtained.

O

T 1

T = N… (1)

N

Therefore, assuming that the number of position feedback pulses output from position detector 3 in one rotation of axis 1 is P rev (number), any rotation speed less than base speed N 1 Calculating the number of pulses P 1 to be emitted by the position detector 3 from the point of N until the main shaft 乇 overnight 4 is rotated along the deceleration straight line L to the command stop position is calculated. Vertical broken line and deceleration line L and horizontal Since the area of a small triangle divided by the time axis, which is the axis, is equal to the number of rotations of the main shaft before stopping, it is expressed by the following equation.

1 N

P 1 = T P rev (2

2 6 0

Then, from the above equation and equation (2), the following equation is obtained.

P rev T

P 1 = N 3

1 2 0 N 1

Then, when the above equation (3) is solved for the rotation speed N, the following equation is obtained.

4 Here, if the output torque of the motor in the constant torque region is T m, the motor inertia is J m, and the load inertia is JL, the following equation is obtained from the general equations of torque and acceleration. Is established.

J m + J L 2 π

Τ 1 = Ν 1

Τ m 6 0

5 From the above equation (5), the following equation is obtained.

T m 6 0

J m -r JL 2 π … (6) Furthermore, substituting the above equation (6) for the left side into the right side of the equation (4),

2 0 T m 6 0

N = P

P rev J m + J L 2 π

… (7) In the above equation (7), the output torque Tm for one night, 乇 —the inertia Jm, the load inertia JL, and the number of pulses P rev per revolution of the main shaft 1 are known. Therefore, part of equation (7) is parametrized as follows according to the characteristics of the model.

(8) Write the value of the parameter P RM in equation (8) in the ROM of the motor control circuit 7 in advance.

Therefore, by using the above equation (8), equation (7) can be expressed by the following equation.

The content of this equation (9) means that, at the current speed N, the position command of the pulse number P 1 is given as the initial value of the position deviation, and from this position deviation, the position feed knock pulse P f is subtracted to obtain the position deviation, and a parameter is added to the square root of the position deviation. -Evening position loop control, which calculates the speed command by multiplying the square root of the PRM as the position loop gain, means that the most efficient deceleration operation was performed until the stop. This means that the spindle motor 4 will be stopped along the deceleration line L in Fig. 4.

When equation (9) is solved for the number of pulses P 1 of the moving distance to the stop, the following equation is obtained.

P 1 = N 'N / PRM-(1-0) The meaning of this (10) equation is that when the rotation speed of the main shaft 乇 overnight 4 is N, the initial value of the position deviation is (1 0 ) Is the number of pulses calculated by the equation ₍ 1) ₍ Accordingly, in order to stop the spindle 1 in a short time while maximizing the deceleration capacity of the spindle motor 4, First, the rotation speed of the spindle motor 4 is reduced to a rotation speed N equal to or lower than the base speed N1, and the number of pulses P1 obtained by the equation (10) at that time is set as the initial value of the position deviation. If the position loop control is performed with the setting, the positioning can be performed in the shortest time at the position of the pulse number P1 from that point.

When the spindle motor 4 is stopped by the positioning stop command, a predetermined position within one rotation of the spindle 1 is commanded as the target position. That is, the target position is instructed in advance as a rotation position at which a predetermined number (P2) of position detection pulses have been issued from the time when the one rotation signal is output.

Here, as shown in Fig. 5, the current spindle is It is assumed that the position detection pulse is at the rotational position (“present”) at which P 0 pulses are output from the time (“signal”) is output. In order for this spindle to rotate from this current position in the forward direction (clockwise in the example of Fig. 5) and the position within one revolution to overlap the above stop position ("stop"), the rotation of the spindle The amount is expressed by the number of position detection pulses cr (<Prev).

As shown in Fig. 5 (a), when P 2 ≥ P 0

α = Ρ 2 — P 0 and

As shown in Fig. 5 (b), in the case of P 2 and P O

a = P2-P0 + Prev.

Therefore, the number of pulses P 1 from the current position to the stop position is obtained by performing the calculation of the expression (10) based on the rotation speed N, and as a result, the value P 1 is smaller than the above value α. In this case (Ρ 1 <α), it means that the speed Ν at that time is smaller than the speed at which the movement amount of the pulse number α is stopped in the shortest time. For the positional deviation given as a value, set the pulse amount α instead of the pulse number Ρ 1 in the error count. Then, the feedback pulse Pf from the position detector is subtracted from the initial position deviation α, and the speed command is calculated by multiplying the square root by a coefficient determined by the overnight deceleration characteristic. (Refer to equation (9) above), and position loop control (switch S1 off in Fig. 2, switch S2 on). Then, the speed once rises from that point onward, but after that, the position is reduced in the shortest time along the deceleration line L. You can decide.

On the other hand, when the value of the pulse number P 1 from the current position to the stop position is equal to or larger than the above value α, (P 1 ≥), 1 or an integer n or more For

+ (n — 1) · P rev <P 1 ≤ α + η · P rev

-•• Set “ct10n · Prev” based on the value of n when (1 1) is satisfied as the initial value of the positional deviation cr '. Then, from this initial position deviation, subtract the feed-no-max and the pulse Pf from the position detector, and multiply the square root by a coefficient determined by the motor deceleration characteristics. Then, calculate the speed command (see equation (9) above), and perform position loop control (switch S1 off and switch S2 on in Fig. 2). Then, the value α 'given as the initial value is equal to or slightly larger than PI, so that the speed may increase slightly from that point in time, but immediately thereafter. After getting on the deceleration line L, the vehicle will reach the final stop position along the deceleration line L in the shortest time without causing an overshoot.

FIG. 3 is a flowchart schematically showing the “fixed-position stop processing” employed in the present embodiment to realize the control method described above. Hereinafter, the embodiment will be described with reference to this flowchart. The method of positioning the spindle will be described.

The processor of the motor control circuit 7 that receives the stop position of the pulse number P 2 from one rotation signal position as the stop position together with the positioning stop command from the numerical controller 8 The processing of the flowchart shown in (1) is performed at predetermined intervals.

First, it is determined whether or not the current rotation speed N of the main shaft motor 4 has reached a rotation speed region equal to or lower than the base speed N 1 (step S 1). If the base speed is not lower than N1, the base speed N1 is output as the rotation speed command Vcmd at predetermined intervals until the rotation speed N becomes lower than or equal to the base speed N1. S 2), the rotational speed N of the spindle motor 4 is reduced to the base speed N 1 or less, that is, the switch S 2 in FIG. 2 is turned off and the switch S 1 is turned on. In the state of, the base speed N1 is continuously output as the rotation speed command Vcmd.

When it is detected in step S1 that the current rotational speed N has become equal to or less than the base speed N1, the processor of the motor control circuit 7 sets the movement amount setting completion flag. It is determined whether or not F is set (step S3).

However, at this stage, since the movement amount setting completion flag F has been reset by the initial setting, the equation (10) is further calculated based on the current rotation speed N, and the deceleration curve is calculated. When the spindle motor 4 is stopped along L, the number of pulses P1 of the amount of rotation that rotates until the spindle motor 4 stops is determined and stored in the register (step S4).

Next, the processor of the motor control circuit 7 determines, from the value of the counter that counts the position feed knock pulse, the value of the counter at the time of detection of one rotation signal latched by the latch circuit. Decrease the value to reduce the spindle rotation from the one-turn signal position at that time. Obtain the position PO, subtract the current position P0 from the positioning stop position P2 within one rotation of the spindle, and obtain the movement pulse amount α (= Ρ2-Ρ0) from the current time to the stop position (Step S 5) If this value is 0 or positive, it is stored as an initial value in the position deviation storage register R (e), and if negative, the number of pulses for one rotation of the spindle is stored in this value. Prev is added and stored as an initial value in the position deviation storage register R (e) (steps S6 to S8). When the value of the pulse number α = P 2 — P 0 obtained in step S5 is positive, the current position Ρ 内 in one rotation of the spindle 1 is positioned with respect to the one rotation signal. Fig. 5 (a) shows a state as shown in Fig. 5 (a) where the positioning stop position Ρ2 has not been reached, and the current position PO of the spindle motor 4 has passed the positioning stop position P2. In the state as in b), that is, when P0> P2 and α is 0 (step S6), the number of rotation pulses P rev of the main shaft 1 corresponding to one rotation of the main shaft 1 is further added. Then, [P 2 — P 0 + P rev = α + P rev] is used as the initial value of the position deviation, and this value is stored in the position deviation storage register R (e) as the initial value. is there.

Next, the processor determines the magnitude of the number of pulses P1 obtained in step S4 and the value stored in the position S deviation storage register R (e), that is, the number of pulses α up to the positioning stop position P2. By comparing the relationships, if the value stored in the register R (e) is equal to or smaller than the determined pulse number P1 (step S9), the register R (e) ) The value obtained by adding the pulse amount Prev for one rotation of the spindle to the value α is stored as a new value in this register R (e) (step S10), and step S9 is executed. Again, the magnitude relationship between the pulse number P 1 and the value α newly stored in the position deviation storage register R (e) is compared again. In this way, the value stored in the register R (e) gradually increases by repeating steps S9 and S10, and finally the register R (e) The flag F is set when the value stored in is larger than the pulse number P 1, that is, when the value of the integer n that satisfies the expression (11) is found. (Step S ll) to start position loop control. That is, the switch S1 in FIG. 2 is turned off, and the switch is switched to the state in which the switch S2 is turned on. Therefore, the position feedback amount Pf in the cycle is subtracted from the position deviation e stored as an initial value in the position deviation storage register R (e) to obtain a new position deviation e. The value is stored in the lever R (e) (step S12), and the square root of the parameter PRM is multiplied by the value of the square root of the positional deviation e and the parameter PRM stored in the register R (e). Then, the speed command Vcmd is obtained (step S13), passed to the speed loop process, and the process of the cycle ends.

From the next cycle, since the movement amount setting completion flag F is set, the steps S1 and S2 and the step S3 are determined from the determination processing of the steps S1 and S3. 13 The processing to shift to 3 is repeated and the position loop processing is executed. Then, it is written in the position deviation storage register R (e). If the memorized value becomes "0", that is, if the position deviation becomes "0", the speed command becomes "0" and the spindle 1 stops.

As described above, the case where the reduction ratio of the power transmission mechanism 2 is 1: 1 (the same applies to the case where the spindle 1 and the spindle motor 4 are directly connected) has been described as one embodiment. Even in a configuration having a reduction ratio, the spindle positioning method of the embodiment can be similarly applied by correcting and using the above-described equations. .

Claims

The scope of the claims

1. When a fixed position stop command is received while the main spindle motor is being driven and controlled based on speed control, the motor speed is controlled based on the speed control to the maximum speed that defines the constant torque area. Reduced to a speed below the base speed,

When the speed is reduced to that speed, the drive control of the motor and motor is changed from the speed control by setting the value related to the current position within one rotation of the motor and the command stop position as the initial position deviation. Switch to position control,

Thereafter, the linear acceleration / deceleration control is executed up to the command stop position.

2. In the spindle positioning method that positions the spindle at the desired rotation position, if the spindle motor falls below the base speed of the maximum rotation speed that defines the constant torque area, the spindle motor speed and the rotation position within one rotation of the spindle are detected. Then, a minimum moving amount for decelerating and stopping along a deceleration straight line set based on the detected speed is obtained, and a moving amount from a detected rotational position to a target stop position is obtained. The movement amount for one rotation of the spindle is sequentially added to the movement IT until the movement amount becomes larger than the small movement amount, and the movement amount obtained by the addition is set as a position deviation, and the square root of the position deviation is calculated. Spindle positioning characterized by performing position loop control by multiplying the set position loop gain to obtain a speed command, and controlling the drive of the spindle motor based on the speed command. Method.

3. The minimum travel distance is the square of the detected speed along the deceleration line 2. The spindle positioning method according to claim 1, wherein said position loop gain is a value of a square root of said parameter, which is obtained by dividing by a preset parameter value determined in advance.

4. Spindle positioning method consisting of the following steps

(a) When a fixed position stop command is received, the rotation speed of the spindle motor is reduced to a speed N below the maximum rotation speed N1 that defines the constant torque area,

() Calculate the number P 1 of output rotation pulses of the position detector when rotating from the reduced rotation speed N to the final stop position at a predetermined constant deceleration,

(c) Calculate the number of output rotation pulses α of the position detector from the current inside rotation position of the spindle to the command stop position of the spindle, and

(d) Compare the number of pulses P1 calculated in (b) above with the number of pulses α calculated in (c) above,

(e) When the pulse number or is larger than the pulse number P 1, the pulse number α is set as the initial position deviation, and the pulse number Ρ 1 is the pulse number α. If it is greater than or equal to, the output rotation pulse number of one revolution of the spindle of the position detector is Prev, and for the integer n of 1 or more,

+ (n— 1) 'P rev <Ρ 1 ≤ α10 η · Ρ When rev is satisfied, set η · P rev as the initial position deviation and set it in the error counter.

(f) After that, the position is calculated from the initial deviation obtained in (c) above. The number of feedback pulses P f from the detector is subtracted, and the speed command is obtained by multiplying the square root of the number of pulses of the subtracted value by the gain determined by the deceleration characteristics of the night. Drive control of the spindle motor based on